Are visitors loving the Grand Canyon to death?
Secret life of the cat: The science of tracking our pets
They share our homes, sleep on our beds and occasionally bring unwanted gifts. Yet, despite our domestic cats playing a big role in our lives, we know surprisingly little about what they get up to. A research project by BBC2's Horizon and the Royal Veterinary College set out to find out more. Alan Wilson, a professor specialising in animal movement, describes what was involved.